Objective To explore the key points and intervention strategies of pharmaceutical care provided by clinical pharmacists for elderly patients with gastrointestinal stromal tumor (GIST) who have multiple comorbidities and are on polypharmacy during imatinib treatment.Methods The clinical pharmacist participated in the management of an elderly patient who developed hematuria and decreased blood glucose levels after imatinib therapy. The causes of these adverse reactions were analyzed, and the pharmacist assisted physicians in evaluating drug interactions and adjusting the treatment regimen.Results After reducing the imatinib dose and discontinuing rivaroxaban, the patient's hematuria gradually resolved. In response to the potential insulin-sensitizing effect of imatinib, adjustments to the insulin dosage prevented any further symptoms of low blood glucose levels.Conclusion By identifying drug interactions and understanding the action characteristics of imatinib, clinical pharmacists provided individualized medication recommendations for elderly patients with complex medication regimens, and emphasized the importance of therapeutic drug monitoring during treatment, reflecting the professional value of pharmacists in optimizing the safety and efficacy of drug therapy for cancer patients.